You can freely build on How Printers Save Toner by Dropping Light-Colored Pixels
This patent expired in 2021. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Ricoh Co Ltd
Patent granted
2002
Expired
2021
Forward citations
9
What this patent covers
This technology manages how a printer uses toner to create an image. It evaluates the darkness of each pixel against a specific threshold. If a pixel is lighter than that threshold, the printer does not print it at all, saving toner. If the pixel is darker than the threshold, the printer uses a Pulse Width Modulation (PWM) pattern, which turns the laser on and off multiple times within a single pixel space to use less toner while still representing the image.
What is now free to use
All 0 claims of US 6476836 are in the public domain. Specifically:
The 0 dependent claims add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
Does not cover methods that reduce toner by globally lowering the laser intensity for the entire page.
Does not cover color-based toner saving that adjusts ink density based on hue rather than pixel brightness.
Does not cover software-based image processing that happens on a computer before the data reaches the printer.
Who is building on this today
Ricoh remains a major player in this space, integrating these types of power and material-saving algorithms into their enterprise multifunction printers. Other major manufacturers like HP and Canon utilize similar PWM-based toner optimization techniques in their standard print drivers.
Products built on expired version of this technology
Toner save mode on office laser printers
Draft print settings in enterprise document management systems
How to cite this patent in your documentation
Ricoh Co Ltd. US Patent 6476836. Image forming apparatus having a function of saving developing agent. Granted 2002, expired 2021. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.